The purpose of this project is to examine the input-output organization of neurons in the motor cortex. Rats have been chosen as the primary experimental animal since they are readily available and have small, lissencephalic brains. Neuroanatomical and neurophysiological techniques are being employed to characterize the first motor cortex (MI) and other closely other related cortical areas in rats and determine their connectional relationships with other neural structures. Immunocytochemical techniques are being used to identify the transmitters of cortical neurons. Neuronal activity will be monitored for several classes of projection neurons in the forelimb area of MI cortex in awake, behaving rats. Intrinsic cortical circuits are being studied by intracellular injection of a tracer, horseradish peroxidase, to visualize the intracortical distribution of neuronal processes of single neurons.